Dry cleaning system for workpieces

ABSTRACT

A system for dry cleaning workpieces by removing solid and/or liquid particles adhereing thereto with a gaseous medium by means of suction. To this end, a suction mold encloses the workpieces on all sides while serving as a guiding device whose inner contour follows the outer contour of the workpiece. The cleaning medium flows to the gaps between the suction mold and the workpiece via feed slots and/or fee boreholes of the suction mold. Gaps, medium fee slots and/or medium feed boreholes are formed, arranged and dimensioned so that the flowing medium has a veloscity of greater than 20 m/s everywhere on the surface of the workiece, and the solid and/or liquid articles adhereing thereto are carried away. The suction slot, through which the flowing medium is removed by suction, and the suction duct which is connected thereto and which leads to the suction unit, has larger cross-sections than the sum of the cross-sections of all the gaps between the workpiece and the suction mold, and also the sum of the cross-sections of the medium feed slots and/or of the mediuum feed boreholes. The sum of the cross-sections of the medium feed slots and or of the medium feed boreholes corresponds to 0.9 to 1.2 times the sum of the cross-sections of all the gars between the workpieces and the suction molds.

The invention relates to a system for dry cleaning of work pieces with agaseous medium, by means of suctioning off solid and/or liquid particlesthat adhere to them, having a suction channel that leads to a suctionunit, and a guide device that precedes the suction channel, by means ofwhich the suction stream in the region of the surface of the work pieceis guided in such a manner that a flow is formed at the surface of thework piece, which entrains the adhering solid and/or liquid particles.

Systems for dry cleaning of work pieces after cutting machining are usedto remove residues or processing aids of the machining process. They areincreasingly replacing wet methods in which solvents are used, fromwhich residues can subsequently be removed only with great effort, if atall, in order to process them as recycled materials. In contrast, afterdry cleaning, the liquid residues, such as emulsions or lubricant oil,can easily be separated from the solid contaminants, such as chips, bymeans of microfilters, and can be used for machining once again.Metallic residues, on the other hand, can be processed as recycledmaterials.

The known dry-cleaning methods of work pieces include the removal of theresidues by means of blowing them off using jets that are directed atthe work piece (see U.S. Pat. No. 4,381,577). It has been shown,however, that the energy expenditure is relatively high, in order toproduce an air volume having the required excess pressure to remove theresidues on the entire surface of the work piece. In order to increasethe effectiveness of the generated air stream, other methodsadditionally use suction systems and/or support the release of theresidues by putting the work piece into vibration or rotation (see DE295 20 880 U1 and DE 196 29 436 A1).

Another method for dry cleaning of work pieces is limited to the use ofsuction systems (see DE 196 29 436 A1 and DE 196 33 771 C2). However,because of the non-uniform flow of the air that is suctioned off,complete cleaning of the work piece on its complex surface is difficultto achieve, and is connected with a significant energy expenditure togenerate a high volume stream and very low pressures. Here, too,additional vibration generators are generally used.

Passing the air flow through a guide plate, as is provided by anothermethod, is also insufficient (see DE 196 29 436 A1). It is true that inthis manner, the flow velocity can generally be increased, if a suitablearrangement is used. However, the suction air takes the path of leastresistance, which means that it follows the contour of the guide plateand not the complex contour of the work piece. A precisely defined flowbehavior at all points of the outside contour of the work piececonsequently does not exist. Here again, additional supportive measures,such as blowing, are required. The stated cleaning device relates to achamber system in which the work piece can furthermore be rotated.Particularly for work pieces having complex surfaces, this means that asufficient distance between the work piece and the guide plate isrequired, and this again puts the flow that is sufficient for thecleaning effect in doubt.

It is therefore the task of the invention to further develop the systemfor dry cleaning of work pieces, of the type stated initially, in such amanner that an optimal flow behavior of a gaseous flow medium is formedon the entire surface of the work piece, and therefore a good cleaningof the work piece is achieved. At the same time, the amount of energyrequired for this is supposed to be decisively reduced.

To accomplish this task, the invention proposes, proceeding from thesystem for dry cleaning of work pieces of the type stated initially,that the guide device is configured as a suction mold that surrounds thework piece on all sides, the inside contour of which follows the outsidecontour of the work piece and leaves defined gaps towards the outsidecontour of the work piece, to which a gaseous medium flows by way offeed slits and/or feed bores in the suction mold, whereby the gaps, onthe one hand, and the medium feed slits and/or medium feed bores, on theother hand, are configured, arranged, and sized in such a manner thatthe flow velocity of the gaseous medium is more than 20 m/s everywhereon the surface of the work piece.

In the system for dry cleaning of work pieces according to theinvention, a suction mold surrounds the work piece to be cleaned. Theinner contours of this suction mold essentially represent the negativeimage of the contours of the work piece. This makes it possible todefine the gaps around the work piece in such a manner that a flowvelocity of the gaseous medium that is proportional to the suctioning isbrought about by means of their cross-section. The distances between thework piece and the suction mold should be 1 mm to 5 mm. The gaseousmedium flows into the gaps between the suction mold and the work piecethrough feed slits and/or feed bores that are made in the suction moldat defined locations. In this way, the flow of the gaseous cleaningmedium is passed to the surface of the work piece in targeted manner.

In order to ensure that the flow medium passes uniformly over the entiresurface of the work piece, both the sum of the cross-sections of thefeed slits and feed bores for the gaseous medium and the sum of thecross-sections of the gaps between the suction mold and the work pieceshould be smaller than the opening cross-section of the suction slitthrough which the gaseous medium leaves the suction mold. The suctionslit must extend at least over the entire length of the work piece. Theaccelerated flow medium entrains solid and/or liquid particles adheringto the work piece. This process is supported by the pressure drop thatoccurs at an increased flow velocity.

The sum of the cross-sections of the feed slits and feed bores at whicha gaseous flow medium enters into the suction mold must permit asufficiently large volume stream. On the other hand, an overly greattotal cross-section can have a detrimental influence on the flowbehavior at the surface of the work piece and result in non-uniformimpact, so that the in-flow velocity at various parts of the work pieceis too low. Under certain conditions, it is advantageous to acceleratethe medium in advance, asit enters into the suction mold, by making theslits and bores appropriately small. Empirical and mathematical studieshave shown that optimal cleaning effects can be achieved if the sum ofthe cross-sections of the feed slits and feed bores for the gaseousmedium corresponds to 0.9 to 1.2 times the sum of the cross-sections ofall the gaps between the work piece and the suction mold that surroundthe work piece.

From this constellation, the result is obtained that the flow velocityof the gaseous medium is greatest around the work piece. Starting fromthe suction slit, and in the subsequent suction channel, in thedirection of the suction unit, a lower flow velocity occurs with greatcross-sections. It is practical if the connection cross-sections in thesuction channel and to the suction unit itself are additionallyexpanded. This results in calming of the flow, which promotesprecipitation of the heavier particles out of the residues of machiningof the work piece.

The accelerated flow medium in the gap between the suction mold and thework piece entrains the residues from machining of the surface of thework piece. This effect is promoted by the fact that an increasing flowvelocity is accompanied by a pressure drop, so that a partial vacuumoccurs. According to empirical studies, the best results for looseningemulsions, lubricant oil, and other residues from cutting machining canbe expected at flow velocities of at least 20 m/s, for the planned areasof use.

An exemplary embodiment of the invention will be explained in greaterdetail below, using drawings. These show:

FIG. 1: a perspective view of the system according to the invention fordry cleaning of work pieces, in the open state;

FIG. 2: a perspective view of a complete cleaning station with anintegrated dry-cleaning system.

The system for dry cleaning of work pieces 2, as shown, is designed forsecondary processing of crankshafts 22. It consists essentially of thesuction mold, only one half 1 a of which is shown, the pusher plates 12,13 with setting devices 17 a, 17 b, the noise protection hood 21, and abase plate 19.

The suction slit 8, through which the gaseous cleaning medium, in thiscase air, containing the particles released from the crankshaft, asresidues from cutting machining, goes in the direction of a suction unit10, not shown, is located in the base plate 19. Consoles 11 a and 11 b,in which the crankshaft 22 is mounted relative to the system and abovethe suction slit 8, are located on both sides of the suction slit 8.

The suction mold 1, only one half 1 a of which is shown here, is pushedtogether for the cleaning process, so that it surrounds the crankshaft22. For this purpose, the suction mold 1 is provided with insidecontours 4 a, 4 b, and 4 c, into which the cropped parts 23 of thecrankshaft 22, which is aligned relative to the suction mold 1, projectwith their outside contours 5 a, 5 b, and 5 c. Only a distance of 1 to 5mm remains between the suction mold 1 and the crankshaft 22, in thestate closed for cleaning. Feed slits 6 and feed bores 7 made in thesuction mold 1 serve to distribute the gaseous flow medium in targetedmanner, and thereby to supply it even to the cropped parts 23 of thecrankshaft surface that project into the suction mold 1.

The suction mold halves 1 a, 1 b can be mounted on the pusher plates 12,13, by means of pins 24, in bores prepared for that purpose, so thatthey can be easily replaced. In this way, the dry-cleaning system canquickly and easily be re-fitted for work pieces other than thecrankshaft 2 having different shapes and dimensions, for examplecamshafts or also crankshafts for engines having different numbers ofcylinders.

The pusher plates 12, 13 are guided on rails 16 a, 16 b so that they canbe displaced. For this purpose, setting devices 17 a, 17 b are attachedto the supporting construction 26 of the system with their staticallyfixed end 25 a, and attached to the pusher plates 12, 13 with their end25 b that can move out, by way of stirrups 18 a, 18 b. By means ofsynchronization of the setting devices 17 a, 17 b, the pusher plates 12,13 are synchronously moved together, with the suction mold halves 1 a, 1b, and positioned symmetrically to the work piece 2. This ensures thatthe gaps 3 a, 3 b between the inside contour 4 of the suction mold andthe outside contour 5 of the work piece 2 are identical for the suctionmold half 1 a and the suction mold half 1 b.

In the region of the consoles 11 a, 11 b for mounting the crankshaft 22,there are recesses 15 a, 15 b in the pusher plates 12, 13. Because ofthe recesses 14 a, 14 b, the cross-section of the suction slit remainsfree, even if the pusher plates are pushed together for the cleaningprocess.

A two-part noise protection hood 21 a, 21 b is also mounted on thepusher plates 12, 13. It surrounds the suction mold halves 1 a, 1 b andis pushed together, along with them, by means of the pusher plates, insuch a manner that only a defined gap remains for the inflow of air asthe cleaning medium. The noise protection hood 21 a, 21 b can be easilyreplaced, like the suction mold, and is mounted on the pusher plateswith pins 27.

The dry-cleaning system according to the invention is mounted on thesupport frame 28 of a cleaning station, as shown schematically in FIG.2. A collection container 20 below the base plate 19 first collects theresidues from the cleaning medium. Connected with this are two suctionchannels or hoses 9 a, 9 b, through which the cleaning medium gets intoa collection container 29, not shown in detail. A control panel 30having various control and regulation elements allows further settingsfor optimal functioning of the system.

1. System for dry cleaning of work pieces with a gaseous medium, bymeans of suctioning off solid and/or liquid particles that adhere tothem, having a suction channel (9) that leads to a suction unit (10),and a guide device that precedes the suction channel, by means of whichthe suction stream in the region of the surface of the work piece (2) isguided in such a manner that a flow is formed at the surface of the workpiece, which entrains the adhering solid and/or liquid particles,whereby the guide device is configured as a suction mold (1) thatsurrounds the work piece on all sides, the inside contour (4) of whichfollows the outside contour of the work piece (5) and leaves definedgaps (3) towards the outside contour of the work piece, wherein agaseous medium flows to the gaps by way of feed slits (6) and/or feedbores (7) in the suction mold, whereby the gaps (3), on the one hand,and the medium feed slits (6) and/or medium feed bores (7), on the otherhand, are configured, arranged, and sized in such a manner that the flowvelocity of the gaseous medium is more than 20 m/s everywhere on thesurface of the work piece (2).
 2. System as recited in claim 1, whereinthe suction channel (9) is connected with the interior of the suctionmold (1) by way of a suction slit (8) that extends at least over theentire length of the work piece (2).
 3. System as recited in claim 1,wherein the suction slit (8) and the subsequent suction channel (9) havegreater cross-sections, in each instance, than the sum of thecross-sections of all of the gaps (3) between the work piece (2) and thesuction mold (1) surrounding the work piece, and the sum of thecross-sections of the feed slits (6) and feed bores (7) for the gaseousmedium.
 4. System as recited in claim 1, wherein the sum of thecross-sections of the feed slits (6) and feed bores (7) for the gaseousmedium corresponds to 0.9 to 1.2 times the sum of all the gaps (3)between the work piece (2) and the suction mold (1) that surround thework piece.
 5. System as recited in claim 1, wherein the contours (4) ofthe suction mold (1) follow the contours (5) of the work piece (2) witha distance between 1 mm and 5 mm.
 6. System as recited in claim 1,wherein the suction unit (10) has a flat characteristic and works at apartial vacuum of 50 mbar to 100 mbar.
 7. System as recited in claim 1,wherein the suction mold (1) consists of two halves (1 a, 1 b). 8.System as recited in claim 1, wherein the suction mold (1) or thesuction mold halves (1 a, 1 b) are mounted on pusher plates (12, 13)that can be moved relative to the work piece (2), held by holders (18 a,18 b).
 9. System as recited in claim 8, wherein the pusher plates (12,13) have recesses (14 a, 14 b, and 15 a, 15 b) that permit them to bemoved completely into one another and merely leave the suction slit (8)free.
 10. System as recited in claim 8, wherein the pusher plates (12,13) are guided on rails (16 a, 16 b).
 11. System as recited in claim 8,wherein setting devices (17 a, 17 b) are switched synchronously in orderto move the pusher plates (12, 13) with the suction mold halves (1 a, 1b) towards the work piece (2) and the suction slit (8) synchronously,and thereby position the suction mold halves symmetrically to the workpiece.
 12. System as recited in claim 7, wherein the suction mold (1) issurrounded by a noise protection hood (21) during the cleaning process.13. System as recited in claim 12, wherein the noise protection hood(21) consists of two halves (21 a, 21 b), which are mounted on themovable pusher plates (12, 13), like the suction mold halves (1 a, 1 b).14. System as recited in claim 13, wherein the noise protection hood(21) permits the inflow of a gaseous medium.